JP2021095597A - Variation amount prediction method of bath surface position of hot dip metal bath and manufacturing method of hot dip metal plated steel plate - Google Patents

Abstract

To provide a variation amount prediction method of a bath surface position of a hot-dip bath capable of precisely predicting the bath surface position of the hot-dip metal bath.SOLUTION: An variation amount prediction method of a bath surface position of a hot-dip metal bath according to the invention includes a step where a variation amount of a bath surface position accompanied by feeding a metal ingot is calculated by using a first model equation for calculating a variation amount of the bath surface position when the metal ingot is being molten and a second model equation for calculating the variation amount of the bath surface position after the metal ingot is molten. The first model equation and the second model equation include a term expressing the variation amount of the bath surface position by a metal ingot volume and a feeder arm volume, a term expressing the variation amount of the bath surface position by taking a molten metal out by a steel plate, and the variation amount of the bath surface position by a thermal expansion of the molten metal.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for predicting the amount of fluctuation in the bath surface position of a molten metal bath and a method for manufacturing a molten metal plated steel sheet.

In a hot-dip metal plating line such as hot-dip galvanizing, which is a cold-rolled surface treatment line, metal plating is performed by passing a steel plate through a pot accommodating a hot-dip metal plating bath. In such a molten metal plating line, a metal ingot of a molten metal plating bath component such as zinc is put into a pot in order to replenish the consumed molten metal. When the position became less than a predetermined value, the metal ingot of the molten metal plating bath component was charged in one step in a batch process. However, when the metal ingot of the molten metal plating bath component is added in one step, the position of the bath surface fluctuates greatly, which causes ash defects. Against this background, Patent Document 1 proposes a method of adding zinc ingot by calculating the immersion amount of zinc ingot from the dissolution time of zinc ingot and the amount of zinc consumed. According to this method, by controlling the immersion amount of the zinc ingot so that the position of the bath surface immediately before the addition of the zinc ingot and the position of the bath surface after the dissolution of the zinc ingot match, the zinc ingot to be charged at one time can be used. The amount can be suppressed to minimize the amount of fluctuation in the bath surface position.

Japanese Unexamined Patent Publication No. 11-50216

However, even with the method described in Patent Document 1, when the amount of molten zinc consumed is large, the amount of immersion of the zinc ingot is large, so that the amount of fluctuation in the bath surface position is large. Therefore, in order to solve such a problem, it is conceivable to use pitch injection control in which the zinc ingot is immersed in a plurality of stages. However, an excessive increase in the number of pitch input stages leads to wear of the contactor contacts used for input control of the zinc ingot. Therefore, in order to determine the optimum number of pitch injection stages that can control the fluctuation amount of the bath surface position within a predetermined range while suppressing the wear of the contactor contact, the fluctuation amount of the bath surface position due to the injection of the zinc ingot. It was expected to provide a technology that can accurately predict.

The present invention has been made in view of the above problems, and an object of the present invention is to accurately predict the amount of change in the bath surface position of the molten metal bath due to the introduction of the metal ingot. The purpose is to provide a quantity prediction method. Another object of the present invention is to manufacture a molten metal-plated steel sheet capable of producing a molten metal-plated steel sheet while suppressing wear of contactor contacts and controlling the amount of fluctuation of the bath surface position of the molten metal bath within a predetermined range. To provide a method.

In the method for predicting the amount of fluctuation in the bath surface position of the molten metal bath according to the present invention, a steel plate is placed in the pot while replenishing the molten metal by charging a metal ingot into the molten metal bath in the pot using a throwing machine arm. A method for predicting the amount of fluctuation in the bath surface position of a molten metal bath in a continuous molten metal plating apparatus that applies a metal plating treatment to the steel plate by passing the plate through the metal ingot. Using the first model formula for calculating the fluctuation amount of the bath surface position when the metal ingot is being melted and the second model formula for calculating the fluctuation amount of the bath surface position after the metal ingot is melted, The first model formula and the second model formula include a step of calculating the amount of fluctuation of the bath surface position due to the charging of the metal ingot, and the first model formula and the second model formula include the volume of the bath surface position according to the volume of the metal ingot and the throwing machine arm. The term includes a term indicating the amount of fluctuation, a term indicating the amount of fluctuation of the bath surface position due to the molten metal being taken out by the steel plate, and a term indicating the amount of fluctuation of the bath surface position due to thermal expansion of the molten metal.

It is desirable that the first model formula includes a term indicating the amount of change in the bath surface position due to the volume increase accompanying the change of the metal ingot from a solid to a liquid.

The method for producing a hot-dip metal-plated steel sheet according to the present invention uses the method for predicting the amount of change in the bath surface position of the molten metal bath according to the present invention, and the amount of change in the bath surface position due to a change in the number of pitch-inserted stages of the metal ingot. This includes a step of calculating the change, selecting the minimum number of pitch injection stages from the number of pitch injection stages in which the amount of fluctuation of the bath surface position is within a predetermined range, and charging the metal ingot into the pot with the selected number of pitch injection stages.

According to the method for predicting the fluctuation amount of the bath surface position of the molten metal bath according to the present invention, the fluctuation amount of the bath surface position of the molten metal bath due to the introduction of the metal ingot can be accurately predicted. Further, according to the method for manufacturing a hot-dip metal-plated steel sheet according to the present invention, the hot-dip metal-plated steel sheet is manufactured while suppressing the wear of contactor contacts and controlling the fluctuation amount of the bath surface position of the hot-dip metal bath within a predetermined range. be able to.

FIG. 1 is a schematic view showing the configuration of a continuous hot-dip galvanizing apparatus according to an embodiment of the present invention. FIG. 2 is a schematic view showing a zinc ingot charging mechanism. FIG. 3 is a diagram showing the evaluation results of the amount of fluctuation in the bath surface position by the 8-step, 4-step, and 2-step pitch injection control simulation with the hot-dip zinc consumption rate as the average speed. FIG. 4 is a diagram showing the evaluation results of the bath surface position fluctuation amount by the 8-step, 4-step, and 2-step pitch injection control simulation with the hot-dip zinc consumption rate as the maximum speed.

Hereinafter, the configuration of the continuous hot-dip galvanizing apparatus according to the embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic view showing the configuration of a continuous hot-dip galvanizing apparatus according to an embodiment of the present invention. As shown in FIG. 1, the continuous hot-dip galvanizing apparatus 1 according to the embodiment of the present invention includes a snout 2 and a hot-dip zinc pot 3. In this continuous hot-dip galvanizing apparatus 1, the steel sheet S is heat-treated in a continuous annealing furnace (not shown), and then guided into the hot-dip galvanizing bath 4 in the hot-dip zinc pot 3 via a snout 2 for galvanizing. After that, the steel plate S is guided above the hot-dip zinc pot 3 by being turned by the sink roll 5 in the hot-dip zinc pot 3, and after the zinc plating adhesion amount is adjusted by the gas wiping nozzle 6, the next step is performed. Is guided.

Further, the continuous hot-dip galvanizing apparatus 1 is provided with a zinc ingot 10 charging mechanism for replenishing the consumed hot-dip zinc. FIG. 2 is a schematic view showing a zinc ingot charging mechanism. As shown in FIG. 2, in this zinc ingot loading mechanism, the zinc ingot 10 is transported to the loading carriage 22 by the conveyor 21, and then transported to the transport carriage 23 by the loading carriage 22. Then, the zinc ingot 10 is conveyed to the standby position P1 by the transport carriage 23, and then is charged into the ingot box 11 communicating with the hot-dip zinc pot 3 by the throwing machine arm 24. As a result, the zinc ingot 10 is melted in the ingot box 11, and the hot-dip zinc pot 3 can be replenished with hot-dip zinc.

By the way, in the continuous hot-dip galvanizing apparatus 1 having such a configuration, when the zinc ingot 10 is put into the ingot box 11 in one step, the bath surface position 4a of the hot-dip zinc bath 4 fluctuates greatly, and ash defects occur. It becomes a factor. Therefore, in the present embodiment, the control device 30 configured by an information processing device such as a computer dispenses the molten zinc by pitch injection control in which the zinc ingot 10 is divided into a plurality of stages (plural pitches) and charged into the ingot box 11. refill.

Specifically, first, the control device 30 uses the following mathematical formulas (1) and (2) to predict the amount of fluctuation of the bath surface position 4a due to the introduction of the zinc ingot 10 (first model formula, second model formula). Using the model formula), a pitch input control simulation is executed for a plurality of different pitch input stages, and a change in the amount of fluctuation of the bath surface position 4a due to a change in the number of pitch input stages is calculated. Here, the mathematical formula (1) shows a prediction model formula of the fluctuation amount of the bath surface position 4a when the zinc ingot 10 is being dissolved, and the mathematical formula (2) is the bath surface position 4a after the zinc ingot 10 is dissolved. The prediction model formula of the fluctuation amount is shown.

The physical quantities indicated by the parameters in the formulas (1) and (2) are as shown in Table 1 below. In Table 1, the actual amount of adhesion on the front side and the actual amount of adhesion on the back side mean the amount of galvanized adhesion on the surfaces of the steel sheet S on the ingot box 11 side and the opposite side. Further, the parameter β in the mathematical formulas (1) and (2) is a constant value obtained by an experiment. Further, in the mathematical formulas (1) and (2), the first term on the right side is the amount of fluctuation of the bath surface position 4a depending on the volume of the zinc ingot 10 and the throwing machine arm 24, and the second term on the right side is the hot-dip galvanized iron by the steel plate S. The amount of change (hot-dip zinc consumption rate) of the bath surface position 4a due to being taken out is shown. Further, the third term on the right side of the formula (1) is the amount of change in the bath surface position 4a due to the volume increase accompanying the change of the zinc ingot 10 from a solid to a liquid, and the fourth term on the right side of the formula (1) and the formula. The third term on the right side of (2) indicates the amount of change in the bath surface position 4a due to thermal expansion of molten zinc. The third term on the right side of the mathematical formula (1) may be omitted. Further, a correction term indicating the amount of fluctuation of the bath surface position 3a due to the dross removing operation may be added to the mathematical formula (2).

Next, the control device 30 selects the minimum number of pitch input stages from the number of pitch input stages in which the amount of fluctuation of the bath surface position 4a is within a predetermined range, and inserts the zinc ingot 10 into the ingot box 11 with the selected number of pitch input stages. Put it in. According to such a configuration, the galvanized steel sheet can be manufactured while suppressing the wear of the contactor contact and suppressing the fluctuation amount of the bath surface position 4a due to the introduction of the zinc ingot 10 within a predetermined range.

3 (a) to 3 (c) are diagrams showing the evaluation results of the amount of change in the bath surface position by the 8-step, 4-step, and 2-step pitch injection control simulation with the hot-dip zinc consumption rate as the average speed.
FIGS. 4 (a) to 4 (c) are diagrams showing the evaluation results of the amount of change in the bath surface position by the 8-step, 4-step, and 2-step pitch injection control simulation with the hot-dip zinc consumption rate as the maximum speed. As shown in FIGS. 3 and 4, the fluctuation amount (variation amount H) of the bath surface position (bath level) was the smallest in the eight-step pitch input control (FIGS. 3 (a) and 4 (a)). .. However, there is no big difference in the amount of fluctuation of the bath surface position between the 8-step pitch throw-in control and the 4-step pitch throw-in control (FIGS. 3 (b) and 4 (b)), while the 2-step pitch feed control is performed. The amount of fluctuation in the bath surface position can be suppressed as compared with (FIGS. 3 (c) and 4 (c)). Therefore, considering the wear of the contactor contacts, it can be concluded that the four-stage pitch input control is the optimum number of input stages. From this, it was confirmed that the hot-dip galvanized steel sheet can be manufactured while suppressing the wear of the contactor contact and suppressing the fluctuation amount of the bath surface position due to the addition of the zinc ingot within a predetermined range by the four-step pitch injection control. ..

Although the embodiment to which the invention made by the present inventor is applied has been described above, the present invention is not limited by the description and the drawings which form a part of the disclosure of the present invention according to the present embodiment. That is, other embodiments, examples, operational techniques, and the like made by those skilled in the art based on the present embodiment are all included in the scope of the present invention.

1 Continuous hot-dip galvanizing device 2 Snout 3 Hot-dip galvanized pot 4 Hot-dip zinc bath 5 Sink roll 6 Gas wiping nozzle 10 Zinc ingot 11 Ingot box 21 Conveyor 22 Input trolley 23 Transport trolley 24 Input machine arm 30 Control device S Steel plate

Claims (3)

Continuous molten metal plating in which a metal ingot is charged into a molten metal bath in a pot using a throwing machine arm to replenish the molten metal, and a steel plate is passed through the pot to perform metal plating on the steel plate. It is a method for predicting the fluctuation amount of the bath surface position of the molten metal bath in the apparatus, which predicts the fluctuation amount of the bath surface position of the molten metal bath.
The first model formula for calculating the fluctuation amount of the bath surface position when the metal ingot is being melted, and the second model formula for calculating the fluctuation amount of the bath surface position after the metal ingot is melted. Including the step of calculating the amount of change in the bath surface position due to the introduction of the metal ingot by using the metal ingot.
The first model formula and the second model formula are terms indicating the amount of change in the bath surface position depending on the volume of the metal ingot and the throwing machine arm, and the bath surface position due to the molten metal being taken out by the steel plate. A method for predicting the amount of change in the bath surface position of a molten metal bath, which comprises a term indicating the amount of fluctuation of the molten metal and a term indicating the amount of change in the bath surface position due to thermal expansion of the molten metal. The molten metal bath according to claim 1, wherein the first model formula includes a term indicating the amount of change in the bath surface position due to a volume increase accompanying the change of the metal ingot from a solid to a liquid. Bath surface position fluctuation amount prediction method. Using the method for predicting the amount of change in the bath surface position of the molten metal bath according to claim 1 or 2, the change in the amount of change in the bath surface position due to the change in the number of pitch feeding stages of the metal ingot is calculated, and the bath surface is calculated. Molten metal plating including a step of selecting the minimum number of pitch injection stages from the number of pitch input stages in which the amount of position fluctuation is within a predetermined range and charging the metal ingot into the pot with the selected number of pitch input stages. Method of manufacturing steel plate.

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